6. National Institute of Health Stroke Scale (NIHSS) score of ≥ 6 but < 20 at the time of screening and infusion. Subject should not have shown rapid improvement (≥ 8 point decrease) or deterioration (≥ 4 point increase) in the score from time of initial evaluation to pre-infusion. To the extent possible, the time from initial screening evaluation to reevaluation will be at least 24 hours.